The field of the invention relates generally to turbine engines, and more specifically, to methods and systems for cooling fluid in a turbine engine.
At least some known turbine engines use heat exchangers to cool oil that is used during engine operations. Specifically, oil from the engine or its generators is channeled through elements in the heat exchanger, and air from a turbine fan is channeled past the heat exchanger elements to cool the oil. Generally, known heat exchangers include an inlet plenum including a diffuser, a heat exchanger block that includes the heat exchanger elements, and an outlet plenum that may include a plurality of passages that may include valve controls. During operation, fan air is channeled into the inlet plenum and through the heat exchanger block prior to being discharged through the outlet plenum. Oil flowing through the heat exchanger elements is cooled by the fan air. In at least some known turbine aircraft engines, the inlet plenum of the heat exchanger is positioned to receive high pressure air discharged from the fan, and the outlet plenum is positioned to facilitate exhausting the high pressure air outboard. In other known turbine aircraft engines, the inlet and the outlet plenums are both coupled to an engine casing, such that high pressure air discharged from the fan is channeled through the heat exchanger prior to being discharged into the fan air or onto engine compartments.
As is known, the heat transfer capability of the heat exchanger is the greatest in regions having a high heat transfer coefficient, which generally have a significant overlap with regions of local high static pressure defined along the inner walls of the heat exchanger. However, the total pressure of flow passing through the heat exchanger may be decreased due to drag created by the inlet and outlet plenums, and due to passageways formed between the heat exchanger elements. Accordingly, within heat exchangers, high heat transfer capability areas may not be capitalized and therefore, the amount of heat transfer may be reduced.